I'm a bit late to this thread, but I think you have a good idea, Jonas. I think it would work, and last quite a few years.
Since I don't have an SWG in my system (yet --considering it though!) I can't say anything about the metal frame rusting. Yes I know you are not using that, but that was one of your concerns with the original frame. So far, starting my 4th year with my pool partially buried, my posts appear to be doing good.
Rust or corrosion will still be a concern for any fasteners you will be using in this environment. What measures are you taking to mitigate this? I ask because this will be your most likely failure point for the pool. You know that if one fails, the added stress on the adjacent fasteners will likely cause them to fail quickly. This goes for the fasteners for the deck structure as well.
Good luck with this!